Integrated touch and display architectures for self-capacitive touch sensors

ABSTRACT

A self-capacitive touch sensor panel configured to have a portion of both the touch and display functionality integrated into a common layer is provided. The touch sensor panel includes a layer with circuit elements that can switchably operate as both touch circuitry and display circuitry such that during a touch mode of the device the circuit elements operate as touch circuitry and during a display mode of the device the circuit elements operate as display circuitry. The touch mode and display mode can be time multiplexed. By integrating the touch hardware and display hardware into common layers, savings in power, weight and thickness of the device can be realized.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is continuation of U.S. application Ser. No.15/039,400, filed May 25, 2016, which is a National Phase applicationunder 35 U.S.C. § 371 of International Application No.PCT/US2014/058367, filed Sep. 30, 2014, which claims the prioritybenefit of U.S. Application No. 61/916,029, filed Dec. 13, 2013, thecontents of which are hereby incorporated by reference in theirentireties for all intended purposes.

FIELD OF THE DISCLOSURE

This relates generally to touch sensor panels that are integrated withdisplays, and more particularly, to integrated touch sensors/displays inwhich a self-capacitance touch sensor is utilized to detect the presenceof an object in contact with or in close proximity to a touch sensorpanel.

BACKGROUND

Many types of input devices are presently available for performingoperations in a computing system, such as buttons or keys, mice,trackballs, joysticks, touch sensor panels, touch screens and the like.Touch screens, in particular, are becoming increasingly popular becauseof their ease and versatility of operation as well as their decliningprice. Touch screens can include a touch sensor panel, which can be aclear panel with a touch-sensitive surface, and a display device such asa liquid crystal display (LCD) that can be positioned partially or fullybehind the panel so that the touch-sensitive surface can cover at leasta portion of the viewable area of the display device. Touch screens canallow a user to perform various functions by touching the touch sensorpanel using a finger, stylus or other object at a location oftendictated by a user interface (UI) being displayed by the display device.In general, touch screens can recognize a touch and the position of thetouch on the touch sensor panel, and the computing system can theninterpret the touch in accordance with the display appearing at the timeof the touch, and thereafter can perform one or more actions based onthe touch. In the case of some touch sensing systems, a physical touchon the display is not needed to detect a touch. For example, in somecapacitive-type touch sensing systems, fringing electrical fields usedto detect touch can extend beyond the surface of the display, andobjects approaching near the surface may be detected near the surfacewithout actually touching the surface.

Capacitive touch sensor panels can be formed from a matrix ofsubstantially transparent conductive plates made from materials such asindium Tin Oxide (ITO). It is due in part to their substantialtransparency that capacitive touch sensor panels can be overlaid on adisplay to form a touch screen, as described above. Some touch screenscan be formed by, partially integrating touch sensing circuitry into adisplay pixel stackup (i.e., the stacked material layers forming thedisplay pixels).

SUMMARY

The following description includes examples of integrated touch screensincluding touch pixels formed of circuit elements of a liquid crystaldisplay (LCD) or organic light emitting diode (OILED), In an LCDdisplay, the common electrodes (Vcom) in the TFT layer can be utilizedduring a touch sensing operation to form touch pixels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C illustrate an example mobile telephone, an example mediaplayer, and an example portable computing device that can each includean example touch screen according to examples of the disclosure.

FIG. 2 is a block diagram of an example computing system thatillustrates one implementation of an example touch screen according toexamples of the disclosure.

FIG. 3 illustrates an exemplary electrical circuit corresponding to aself-capacitance touch sensor electrode and sensing circuit according toexamples of the disclosure.

FIG. 4 illustrates exemplary layers of an LCD display screen stack-upaccording to some disclosed examples.

FIG. 5 illustrates an exemplary stack-up layer that can be used as bothtouch circuitry and display circuitry according to examples of thedisclosure.

FIGS. 6A-6D illustrate exemplary wire routing schemes for an integratedtouch and display layer according to examples of the disclosure.

FIG. 6E illustrates an exemplary routing connecting for a single touchpixel according to examples of the disclosure.

FIGS. 6F-6I illustrate additional wire routing schemes for an integratedtouch and display layer according to examples of the disclosure.

FIG. 7 illustrates an exemplar), OLED display circuit according toexamples of the disclosure.

FIG. 8 illustrates an exemplary OLED display stack-up according toexamples of the disclosure.

FIG. 9 illustrates a close up view of a portion of the exemplarystack-up of FIG. 8.

FIG. 10 illustrates an integrated OLED display and self-capacitive touchsensor circuit according to examples of the disclosure.

FIG. 11 illustrates an exemplary bootstrapping circuit for an integratedtouch sensor and OLED display according to examples of the disclosure.

FIG. 12 illustrates an integrated on-cell touch sensor and OLED displayaccording to examples of the disclosure.

FIG. 13 illustrates an exemplary close up view of the stack-up depictedin FIG. 12.

FIG. 14 illustrates an exemplary time line for operating the device in atouch detection mode and a display operation mode.

DETAILED DESCRIPTION

In the following description of examples, reference is made to theaccompanying drawings which form a part hereof, and in which it is shownby way of illustration specific examples in which examples of thedisclosure can be practiced. It is to be understood that other examplescan be used and structural changes can be made without departing fromthe scope of the examples of this disclosure.

The following description includes examples of integrated touch screensincluding touch pixels formed of circuit elements of a liquid crystaldisplay (LCD) or organic light emitting diode (OLED), In an LCD display,the common electrodes (Vcom) in the TFT layer can be utilized during atouch sensing operation to form touch pixels.

During a display operation, in which an image is displayed on the touchscreen, the Vcom can serve as part of the display circuitry, forexample, by carrying a common voltage to create, in conjunction with apixel voltage on a pixel electrode, an electric field across the liquidcrystal. During a touch sensing operation, a group of Vcom electrodescan be used to form touch pixel electrodes that are coupled to sensecircuitry to form touch sensors.

FIGS. 1A-1C show example systems in which a touch screen according toexamples of the disclosure may be implemented. FIG. 1A illustrates anexample mobile telephone 136 that includes a touch screen 124. FIG. 1Billustrates an example digital media player 140 that includes a touchscreen 126. FIG. 1C illustrates an example portable computing device 144that includes a touch screen 128. Touch screens 124, 126, and 128 can bebased on self-capacitance. A self-capacitance based touch system caninclude a matrix of small, individual plates of conductive material thatcan be referred to as touch pixel electrodes (as described below withreference to touch screen 220 in FIG. 2). For example, a touch screencan include a plurality of individual touch pixel electrodes, each touchpixel electrode identifying or representing a unique location on thetouch screen at which touch or proximity (i.e., a touch or proximityevent) is to be sensed, and each touch pixel electrode beingelectrically isolated from the other touch pixel electrodes in the touchscreen/panel. Such a touch screen can be referred to as a pixelatedself-capacitance touch screen. During operation, a touch pixel electrodecan be stimulated with an AC waveform, and the self-capacitance toground of the touch pixel electrode can be measured. As an objectapproaches the touch pixel electrode, the self-capacitance to ground ofthe touch pixel electrode can change. This change in theself-capacitance of the touch pixel electrode can be detected andmeasured by the touch sensing system to determine the positions ofmultiple objects when they touch, or come in proximity to, the touchscreen. In some examples, the electrodes of a self-capacitance basedtouch system can be formed from rows and columns of conductive material,and changes in the self-capacitance to ground of the rows and columnscan be detected, similar to above. In some examples, a touch screen canbe multi-touch, single touch, projection scan, full-imaging multi-touch,capacitive touch, etc.

In contrast to self-capacitance based touch systems, a mutualcapacitance based touch system can include, for example, drive regionsand sense regions, such as drive lines and sense lines. For example,drive lines can be formed in rows while sense lines can be formed incolumns (e.g., orthogonal). Mutual capacitance touch pixels can beformed at the intersections of the rows and columns. During operation,the rows can be stimulated with an AC waveform and a mutual capacitancecan be formed between the row and the column of the mutual capacitancetouch pixel. As an object approaches the mutual capacitance touch pixel,some of the charge being coupled between the row and column of themutual capacitance touch pixel can instead be coupled onto the object.This reduction in charge coupling across the mutual capacitance touchpixel can result in a net decrease in the mutual capacitance between therow and the column and a reduction in the AC waveform being coupledacross the mutual capacitance touch pixel. This reduction in thecharge-coupled AC waveform can be detected and measured by the touchsensing system to determine the positions of multiple objects when theytouch the touch screen. Thus, a mutual capacitance based touch systemcan operate differently than a self-capacitance based touch system, theoperation of which was described above.

FIG. 2 is a block diagram of an example computing system 200 thatillustrates one implementation of an example touch screen 220 accordingto examples of the disclosure. Computing system 200 could be includedin, for example, mobile telephone 136, digital media player 140,portable computing device 144, or any mobile or non-mobile computingdevice that includes a touch screen. Computing system 200 can include atouch sensing system including one or more touch processors 202,peripherals 204, a touch controller 206, and touch sensing circuitry(described in more detail below) Peripherals 204 can include, but arenot limited to, random access memory (RAM) or other types of memory orstorage, watchdog timers and the like. Touch controller 206 can include,but is not limited to, one or more sense channels 208, channel scanlogic 210 and driver logic 214. Channel scan logic 210 can access RAM212, autonomously read data from the sense channels and provide controlfor the sense channels. In addition, channel scan logic 210 can controldriver logic 214 to generate stimulation signals 216 at variousfrequencies and phases that can be selectively applied to the touchpixel electrodes of touch screen 220, as described in more detail below.In some examples, touch controller 206, touch processor 202 andperipherals 204 can be integrated into a single application specificintegrated circuit (ASIC).

Computing system 200 can also include a host processor 228 for receivingoutputs from touch processor 202 and performing actions based on theoutputs. For example, host processor 228 can be connected to programstorage 232 and a display controller, such as an LCD driver 234. The LCDdriver 234 can provide voltages on select (gate) lines to each pixeltransistor and can provide data signals along data lines to these sametransistors to control the pixel display image as described in moredetail below. Host processor 228 can use LCD driver 234 to generate animage on touch screen 220, such as an image of a user interface (UI),and can use touch processor 202 and touch controller 206 to detect atouch on or near touch screen 220. The touch input can be used bycomputer programs stored in program storage 232 to perform actions thatcan include, but are not limited to, moving an object such as a cursoror pointer, scrolling or panning, adjusting control settings, opening afile or document, viewing a menu, making a selection, executinginstructions, operating a peripheral device connected to the hostdevice, answering a telephone call, placing a telephone call,terminating a telephone call, changing the volume or audio settings,storing information related to telephone communications such asaddresses, frequently dialed numbers, received calls, missed calls,logging onto a computer or a computer network, permitting authorizedindividuals access to restricted areas of the computer or computernetwork, loading a user profile associated with a user's preferredarrangement of the computer desktop, permitting access to web content,launching a particular program, encrypting or decoding a message, and/orthe like. Host processor 228 can also perform additional functions thatmay not be related to touch processing.

Touch screen 220 can include touch sensing circuitry that can include acapacitive sensing medium having a plurality of electrically isolatedtouch pixel electrodes 222 (e.g., a pixelated self-capacitance touchscreen). Touch pixel electrodes 222 can be driven by stimulation signals216 from driver logic 214 through touch interfaces 224 a and 224 b, andresulting sense signals 217 generated from the touch pixel electrodes222 can be transmitted through a sense interface 225 to sense channels208 (also referred to as an event detection and demodulation circuit) intouch controller 206. The stimulation signal may be an alternatingcurrent (AC) waveform. Labeling the conductive plates used to detecttouch (i.e., touch pixel electrodes 222) as “touch pixel” electrodes canbe particularly useful when touch screen 220 is viewed as capturing an“image” of touch. In other words, after touch controller 206 hasdetermined an amount of touch detected at each touch pixel electrode inthe touch screen, the pattern of touch pixel electrodes in the touchscreen at which a touch occurred can be thought of as an “image” oftouch (e.g. a pattern of fingers touching the touch screen). It isunderstood that while driver logic 214 and sense channels 208 areillustrated as being separate blocks in touch controller 206, in aself-capacitance touch system, the sense channels alone can drive andsense touch pixel electrodes 222, as described in this disclosure.Further, in some examples, touch pixel electrodes 222 can be driven andsensed using the same line (e.g., sense signals 217).

FIG. 3 illustrates an exemplary electrical circuit corresponding to aself-capacitance touch sensor electrode (e.g., touch pixel electrode222) and sensing circuit according to examples of the disclosure.Electrode 302 can have an inherent self-capacitance to ground associatedwith it, and also an additional self-capacitance to ground that isformed only when an object is in proximity to the electrode. Touchelectrode 302 can be coupled to sensing circuit 314. Sensing circuit 314can include an operational amplifier 308, feedback resistor 312,feedback capacitor 310 and an input voltage source 306, although otherconfigurations can be employed. For example, feedback resistor 312 canbe replaced by a switched capacitor resistor in order to minimize anyparasitic capacitance effect caused by a variable feedback resistor. Thetouch electrode can be coupled to the inverting input of operationalamplifier 308. An AC voltage source 306 (Vac) can be coupled to thenon-inverting input of operational amplifier 308. The touch sensorcircuit 300 can be configured to sense changes in the totalself-capacitance of the electrode induced by a finger or object eithertouching or in proximity to the touch sensor panel or touch screen. Theoutput 320 of the touch sense circuit 300 is used to determine thepresence of a proximity event. The output 320 can either be used by aprocessor to determine the presence of a proximity or touch event, oroutput 320 can be inputted into a discrete logic network to determinethe presence of a touch or proximity event.

FIG. 4 illustrates exemplary layers of an LCD display screen stack-upaccording to some disclosed examples. Backlight 404 can provide whitelight that can be directed towards the aperture of the stack-up. As willbe discussed below, the backlight can supply the rest of the displaystack-up with light that can be oriented in particular orientation basedon the needs of the rest of the stack-up. In order to control thebrightness of the light, the white light produced by the backlight 404can be fed into a polarizer 406 that can impart polarity to the light.The polarized light coming out of polarizer 406 can be fed throughbottom cover 408 into a liquid crystal layer 412 that can be sandwichedbetween an Indium Tin Oxide (ITO) layer 415 and a Thin Film Transistor(TFT) layer 410. TFT substrate layer 410 can contain the electricalcomponents necessary to create the electric field, in conjunction withITO layer 414 that drives the liquid crystal layer 412. Morespecifically, TFT substrate 410 can include various different layersthat can include display elements such as data lines, gate lines, TFTs,common and pixel electrodes, etc. These components can help create acontrolled electric field that orients liquid crystals located in liquidcrystal layer 412 into a particular orientation, based on the desiredcolor to be displayed at any particular pixel. The orientation of aliquid crystal element in liquid crystal layer 412 can alter theorientation of the polarized light that is passed through it frombacklight 404. The altered light from liquid crystal layer 412 can thenbe passed through color filter layer 416. Color filter layer 416 cancontain a polarizer. The polarizer in color filter layer 416 caninteract with the polarized light coming from liquid crystal layer 412,whose orientation can be altered depending on the electric field appliedacross the liquid crystal layer. The amount of light allowed to passthrough color filter layer 416 into top cover 418 can be determined bythe orientation of the light as determined by the orientation of theliquid crystal layer 412. While the top cover 418 is described as beingglass, any type of transparent cover can be used including plastic forexample. By polarizing the white light coming out of backlight 404,changing the orientation of the light in liquid crystal layer 412, andthen passing the light through a polarizer in color filter layer 416,the brightness of light can be controlled on a per pixel basis. Colorfilter layer 416 also can contain a plurality of color filters that canchange the light passed through it into red, green and blue. Bycontrolling the brightness and color of light on a per pixel basis, adesired image can be rendered on the display.

Integrating a touch sensor described above in reference to FIG. 3, witha display stack-up described above in reference to FIG. 4 can providemany benefits. For instance, by integrating the touch sensor with thedisplay, the total width of the device can be minimized since the touchand display occupy a common layer. In an architecture in which thedisplay and the touch sensor are mutually exclusive, the total thicknessof the device may be greater. Thus, by integrating the touch anddisplay—in other words, to have the touch sensor occupy one of thelayers in the display stack-up—the total weight and thickness of thedevice can be minimized. In order to integrate layers such that both thetouch sensor panel and the display share a layer, the circuit elementsof a particular layer may be used as both display hardware and touchhardware. The touch functionality and the display functionality of thedevice can be time multiplexed (as will be described below) such thatduring a touch mode, the circuit elements of the common layer can beused as touch circuitry and during a display mode the circuit elementsof the common layer can be used as display circuitry. In some examples,one or more of touch controller 206, touch processor 202 and hostprocessor 228 can control the time multiplexing of the touch and displayfunctionalities of the device.

FIG. 5 illustrates an exemplary stack-up layer that can be used as bothtouch circuitry and display circuitry according to examples of thedisclosure. In the example of FIG. 4, the TFT layer 410 can be modifiedsuch that circuit elements residing on the TFT layer can be used asdisplay circuitry during a display mode of the device and as touchcircuitry during a touch mode of the device. TFT layer 509 can havecircuit elements 511 formed on it. Circuit elements 511 can constitutethe V_(com) layer of a display. Circuit elements 511 can be, forexample, multi-function circuit elements that operate as part of thedisplay circuitry of the touch screen and also as part of the touchsensing circuitry of the touch screen. In some examples, circuitelements 511 can be single-function circuit elements that operate onlyas part of the touch sensing system. In addition to circuit elements511, other circuit elements (not shown) can be formed on TFT glass 509,such as transistors, capacitors, conductive vias, data lines, gatelines, etc. Circuit elements 511 and the other circuit elements formedon TFT glass 509 can operate together to perform various displayfunctionality required for the type of display technology used by touchscreen 220, as one skilled in the art would understand. The circuitelements can include, for example, elements that can exist inconventional LCD displays. It is noted that circuit elements are notlimited to whole circuit components, such a whole capacitor, a wholetransistor, etc., but can include portions of circuitry, such as onlyone of the two plates of a parallel plate capacitor.

During a touch mode of the device, some or all of the circuit elements511 can be electrically connected to sense circuitry such that eachcircuit element can be used as a touch pixel electrode with the circuitconfiguration illustrated in FIG. 3, The circuit elements 511 can act aselectrodes 302 in the circuit configuration of FIG. 3 during a touchdetection mode of the device. During a display mode of the device, thecircuit elements 511 can be configured such that they act as platecapacitors biased at a common voltage in an LCD display as in known inthe art.

FIG. 5 also shows a pixel material 515 disposed between TFT glass 509and a color filter glass (see FIG. 4). Pixel material 515 is shown inFIG. 6 as separate volume regions or cells above the circuit elements511. For example, when the pixel material is a liquid crystal, thesevolume regions or cells are meant to illustrate regions of the liquidcrystal controlled by the electric field produced by the pixel electrodeand common electrode of the volume region or cell under consideration.Pixel material 515 can be a material that, when operated on by thedisplay circuitry of touch screen 220, can generate or control anamount, color, etc., of light produced by each display pixel. Forexample, in an LCD touch screen, pixel material 515 can be formed ofliquid crystal, with each display pixel controlling a volume region orcell of the liquid crystal. In this case, for example, various methodsexist for operating liquid crystal in a display operation to control theamount of light emanating from each display pixel, e.g., applying anelectric field in a particular direction depending on the type of LCDtechnology employed by the touch screen. In an in-plane switching (WS),fringe field switching (FFS), and advanced fringe field switching (AFFS)LCD displays, for example, electrical fields between pixel electrodesand common electrodes (Vcom) disposed on the same side of the liquidcrystal can operate on the liquid crystal material to control the amountof light from a backlight that passes through the display pixel. Oneskilled in the art would understand that various pixel materials can beused, depending on the type of display technology of the touch screen.

Using circuit elements 511 as touch pixel electrodes can create wirerouting issues, since each circuit element may need to be individuallyconnected to a touch controller so that each touch pixel electrode isconnected to a sense circuit that can detect changes in aself-capacitance of the pixel caused by a finger or object in contactwith or in close proximity to the touch sensor panel. FIG. 6aillustrates a wire routing scheme for an integrated touch and displaylayer according to examples of the disclosure. As illustrated, a TFTlayer 600 can be populated with circuit elements 511 that, in someexamples, can act as both a touch pixel electrode in a touch mode and asa LCD display electrode in a display mode of the device. As describedabove, because each and every circuit element 511 may need to beindividually connected to a sense circuit to detect changes inself-capacitance caused by a touch event (e.g., by using a touch signalline, such as lines 602 or 604, connected to touch chips 606 or 610),and because display pixels associated with the circuit elements mayrequire separate wiring for display functionality (e.g., display datalines connecting TFT(s) in a display pixel to display controller chip608), there can be many wires that need to be routed from each pixel toa touch chip or display controller. In some examples, touch signallines, display data lines and circuit elements 511 can be routed andformed in different metal layers than each other. For example, circuitelements 511 can be formed in a first metal layer, display data linescan be routed in a second metal layer, and touch signal lines can berouted in a third metal layer in some examples, either the display datalines or the touch signal lines can be routed in the same layer in whichcircuit elements 511 are formed. The above routing schemes may need tobe “invisible” to the user of the device. In other words, since parts ofthe display are visible to the user, the wire routing scheme may need toavoid occupying “active areas” of the display (i.e., areas that arevisible to the user).

In one example, each circuit element 511 can be connected to a touchcontroller via a wire that can be routed to a touch controller through“non-active” areas of the touch screen. FIG. 6e illustrates an exemplaryrouting connection for a single touch pixel electrode according toexamples of the disclosure. A circuit element 511 can be connected to awire 616 through a via structure 614. The via structure 614 can providea connection point between the circuit element and the wire 616.Referring back to FIG. 6a ; the wire, for example wire 602, can berouted back to a touch chip 606 as illustrated. As discussed above, wire602, which can carry touch signals from circuit element 511 to a touchchip 606/608, can be routed in a different metal layer than the circuitelement 511; thus, via structure 614 can provide for an electricalconnection between circuit element 511 and wire 602. Touch chips 606 and610 can include sense circuitry (e.g., sense channels), as describedabove. In some examples, each circuit element 511 can be assigned itsown, dedicated sense circuitry (e.g., its own sense channel) in touchchips 606/610. In some examples, a single sense circuitry (e.g., asingle sense channel) in touch chips 606/610 can be shared by two ormore circuit elements 511 using, for example, time-multiplexing with oneor more multiplexers. In some examples, each circuit element 511 in acolumn of circuit elements can share a single sense circuitry (e.g., asingle sense channel) using, for example, multiplexing with one or moremultiplexers.

Another consideration in developing a routing scheme is ensuring thateach path between a circuit element and a touch chip has substantiallythe same resistance. If each path between a circuit element 511 and atouch chip 606 or 610 had varying resistance, the RC time constant ofeach path may also vary, thus causing a lack of uniformity in bandwidthand ultimately in the signal to noise ratio of each touch pixelelectrode. One way to ensure uniformity can be to vary the width of thewire 616 based on the distance the wire has to travel between a circuitelement 511 and a touch chip 606 and 610. For example, touch wire 602has to travel from one side of the TFT layer 600 to the opposite side.In contrast, touch wire 604 only has to connect a circuit element 511that is proximal to the touch chip 606. In order to account for thevarying resistance, touch wire 602 can be patterned to be thicker (i.e.,wider) than touch wire 604. In this way, the wide but long wire 602 mayhave substantially the same resistance as the short but narrow wire 604.

During a display operation of the device, the circuit elements 511 maybe driven by a display controller 608. The display controller 608 canroute display control signals to display driver circuit 618. Displaydrive circuit 618 can be disposed on a border region of the device thatis not visible to a user. The display drive circuit 618 can then routethe signals to a wire matrix 612. The wire matrix 612 can be made fromconductive material that may or may not be transparent. The wire matrix612, as illustrated, can be routed such that it does not cross into anactive area of the display. During a touch mode, the device couldutilize wire matrix 612 to transmit touch signals; however, the touchsignals may see an increased routing resistance since each touch pixelelectrode may need to share routing paths with other touch pixelelectrodes.

While touch chips 606 and 610 and display controller 608 are illustratedin FIG. 6a as being three separate chips, other configurations arecontemplated. For example, touch chips 606 and 610 and displaycontroller 608 can be integrated into a single chip or logic circuit, asillustrated in FIG. 6b (integrated touch and display chip 607). In someexamples, the routing from such an integrated touch and display chip tocircuit elements 511 can remain substantially as illustrated in FIG. 6a. In some examples, display controller 608 can be split into two or moreseparate display controller chips, as illustrated in FIG. 6c (splitdisplay controller chips 608 a and 608 b). In such examples, the splitdisplay controller chips can be disposed between touch chips 606 and610, and routing from circuit elements 511 on one side of TFT layer 600(e.g., the left half of the TFT layer) can be connected to one of thesplit display controller chips (e.g., the display controller chip 608 adisposed on the left), while routing from circuit elements on the otherside of the TFT layer (e.g., the right half of the TFT layer) can beconnected to the other of the split display controller chips (e.g., thedisplay controller chip 608 b disposed on the right) routing fromcircuit elements 511 to touch chips 606 and 610 can remain substantiallyas illustrated in FIG. 6a . In some examples, touch chips 606 and 610and the split display controller chips can be disposed in an alternatingmanner (e.g., touch chip 606, display controller chip 608 a, touch chip610, display controller chip 608 b) in such examples, routing fromcircuit elements 511 to the touch and display controller chips can bearranged appropriately. In another example in which display controller608 can be split, touch chips 606 and 610 can be interleaved betweensplit display controller chips, as illustrated in FIG. 6d (split displaycontroller chips 608 a, 608 b and 608 c). For example, displaycontroller 608 can be split into three separate chips. Touch chip 606can be disposed to the right of a first display controller chip 608 a, asecond display controller chip 608 b can be disposed to the right oftouch chip 606, touch chip 610 can be disposed to the right of thesecond display controller chip 608 b, and a third display controllerchip 608 c can be disposed to the tight of touch chip 610 routingbetween circuit elements 511 and the various touch and display chips canbe arranged appropriately. For example, a left-third of circuit elements511 can be routed to the first display controller chip 608 a, amiddle-third of the circuit elements can be routed to the second displaycontroller chip 608 b, and a right-third of the circuit elements can berouted to the third display controller chip 608 c. Routing from circuitelements 511 to touch chips 606 and 610 can remain substantially asillustrated in FIG. 6a . The above examples are illustrative only, anddo not limit the scope of the disclosure. Other configurations of touchand display chips are similarly contemplated, such as configurations inwhich touch chips 606 and 610 are integrated, or split into more thantwo chips. Further, those of ordinary skill in the art will understandthat touch chips 606 and 610 and display controller 608 can be disposedin arrangements different from those illustrated in FIGS. 6a-6d whilestill allowing for proper touch screen operation.

FIGS. 6f-6i illustrate additional wire routing schemes for an integratedtouch and display layer according to examples of the disclosure. Circuitelements 511 can be routed to touch and/or display chips 622, as shown.Touch and/or display chips 622 can correspond to touch chips 606 and 610and/or display controller 608 in FIGS. 6a-6d . It is understood thatthose circuit elements 511 that are illustrated as not being connectedto touch and/or display chips 622 can be connected to those chips orother chips in a manner analogous to that displayed for other circuitelements. Further, touch and/or display chips 622 can be the same chipor different chips. Details of the routing of circuit elements 511 totouch and/or display chips 622 can be similar to as described in FIGS.6a-6e , the details of which will not be repeated here for brevity.

The touch pixel electrode circuit configuration of FIG. 3 is not limitedto being integrated with an LCD display, and could also be integratedinto various other types of displays such as an organic light emittingdiode (OLED) display. FIG. 7 illustrates an exemplary OLED displaycircuit according to examples of the disclosure. The pixel circuit 750can include an OLED element 701 having two terminals (a cathode terminaland an anode terminal), a p-type transistor such as TFT T2 705, and ann-type transistor such as TFT T1 707. The cathode terminal of OLEDelement 701 can be electrically connected to cathode 703. Cathode 703can be the signal line common to a plurality of pixel circuits in thetouch screen, and can correspond to common electrode 401 or 509, forexample. The anode terminal of OLED element 701 can be electricallyconnected to anode 709. OLED element 701 can be connected to cathode 703and anode 709 in such a way as to allow current to flow through the OLEDelement when the voltage at the anode is higher than the voltage at thecathode (i.e., OLED element is on, or “forward biased”). OLED element701 can emit light when it is on. When the voltage at anode 709 is lowerthan the voltage at cathode 703, substantially no current can flowthrough OLED element 701 (i.e., OLED element is off, or “reversebiased”). OLED element 701 can emit substantially no light when it isoff.

Anode 709 can be electrically connected to the drain terminal of T2 705.The gate and source terminals of T2 705 can be capacitively coupled byway of capacitor C_(st) 711, where one terminal of C_(st) can beelectrically connected to the gate terminal of T2 and the other terminalof C_(st) can be electrically connected to the source terminal of T2.The source terminal of T2 705 can further be electrically connected toV_(DD) 713. The gate terminal of T2 705 can further be electricallyconnected to the drain terminal of T1 707. The gate terminal of T1 canbe electrically connected to gate line 715, and the source terminal ofT1 can be electrically connected to data line 717.

FIG. 8 illustrates an exemplary OLED display stack-up according toexamples of the disclosure. As illustrated in FIG. 8, an OLED structurecan include an encapsulation layer 810, a cathode layer 808, an organiclayer 806 that includes organic light emitting diodes, and an anodelayer 804 that can be disposed on top of a TFT glass 802. The stack-upcan further include a polarizer 814, a pressure sensitive adhesive layer816, and a cover glass 818. The cathode layer 808 can contain circuitelements that act as cathodes to an OLED display during a display modeof the device and act as touch pixel electrodes during a touch mode ofthe device.

FIG. 9 illustrates a close up view of a portion of the exemplarystack-up of FIG. 8. The close up view can include a cathode layer 902,an organic layer that includes organic light emitting diodes 910, and ananode layer that includes anodes 904. As illustrated, the cathode layer902 can include individual cathode plates 906 that can function asdescribed above in FIG. 7. Each individual cathode 906 can be connectedto its own diode 910 and its own anode 904.

As illustrated in FIG. 9, a cathode layer made up of conductive platescan look similar to a TFT layer populated with common voltage electrodeson an LCD display as illustrated in FIG. 4. Thus, similar to an LCDdisplay, an OLED display can have its cathode layer integrated with aself-capacitive sensor similar to the LCD display of FIG. 4.

FIG. 10 illustrates an integrated OLED display and self-capacitive touchsensor circuit according to examples of the disclosure. The circuit ofFIG. 10 can be similar to the circuit depicted in FIG. 3. A circuitelement 1002 can be connected to a sense circuit 1014. The sense circuit1014 can be configured to detected changes in a self-capacitance of thecircuit element due to an object touching or in close proximity to it.Sensing circuit 1014 can include an operational amplifier 1008, feedbackresistor 1012, feedback capacitor 1010 and an input voltage source 1006,although other configurations can be employed. For example, feedbackresistor 1012 can be replaced by a switched capacitor resistor in orderto minimize any parasitic capacitance effect caused by a variablefeedback resistor. The touch electrode 1002 can be coupled to theinverting input of operational amplifier 1008. An AC voltage source 1006(Vac) can be coupled to the non-inverting input of operational amplifier1008. The touch sensor circuit 1000 can be configured to sense changesin self-capacitance induced by a finger or object either touching or inproximity to the touch sensor panel. The output 1020 of the touch sensecircuit 1000 can be used to determine the presence of a proximity event.The output 1020 can either be used by a processor to determine thepresence of a proximity or touch event, or output 1020 can be inputtedinto a discrete logic network to determine the presence of a touch orproximity event.

The operational amplifier 1008 can also be coupled to a referencevoltage 1021 at its non-inverting input. Both the reference voltage 1021and the AC voltage source 1006 can be coupled to the non-inverting inputof the operational amplifier 1008 via switches 1016 and 1018respectively. During a touch mode of the device, switch 1018 can beclosed, while switch 1016 can be opened, thus operating the circuit todetect changes in self-capacitance as discussed above. During a displaymode of the device, switch 1016 can be closed, while switch 1016 can beopened, thus biasing the cathode of the OLED structure according to thediscussion above. Switches 1016 and 1018 can be time multiplexed inorder to time multiplex touch and display functionality as discussedabove and as will be further discussed below.

In an integrated touch and OLED display device, during a touch mode, thelight emitting diode may act as a large parasitic capacitance due to thefact that it is not being utilized and is still connected to the touchpixel electrode. The parasitic capacitance caused by the diode may actto limit the bandwidth of the touch detection as well as degrade thesignal to noise ratio. “Bootstrapping” the anode and cathode of thediode may work to limit the parasitic capacitance caused by the diode.FIG. 11 illustrates an exemplary bootstrapping circuit for an integratedtouch sensor and OLED display according to examples of the disclosure.The circuit 1100 can include an integrated touch and display pixel 1114coupled with sense circuitry 1102. The details of the integrated touchand display pixel 114 and sense circuitry 1102 have been previouslydiscussed. In order to bootstrap the anode 1118 and cathode 1112 of thediode, the stimulation voltage of sense circuit 1102 can be transmittedto the source and gate of transistor 1116 via voltage buffers 1108 and1110 respectively. By stimulating the source and gate of transistor 1116with the same AC voltage, the source and the gate are tied together,causing transistor 1116 to act as a short circuit between the source andthe drain. With the source voltage flowing into the drain, the anode1118 can be biased by the same stimulation voltage as the cathode 1112.Having the anode 1118 and the cathode 1112 stimulated by the same ACvoltage can ensure that the DC current across the diode remains constantand thus can work to mitigate any parasitic capacitance effects causedby the diode during a touch sensing mode.

The example above illustrates an integrated “in-cell” touch and display(i.e., the display and touch pixel share a common layer), but a touchsensor can also be integrated into an OLED display using an “on-cell”architecture in which the touch sensor occupies its own layer within thedisplay stack-up. FIG. 12 illustrates an integrated on-cell touch sensorand OLED display according to examples of the disclosure. As illustratedin FIG. 12, an OLED structure can include an encapsulation layer 1210, acathode layer 1212, an organic layer 1214 that includes organic lightemitting diodes, and an anode layer 1216 that can be disposed on top ofa TFT glass 1218. The stack-up can further include an ITO layer 1208that is patterned with the touch pixel electrodes similar to the touchpixel electrode and wiring descriptions discussed above, a polarizer1206, a pressure sensitive adhesive layer 1204, and a cover glass 1202.The cathode layer 1212 can be switchably configured to be coupled to anAC ground during a touch mode so as to minimize parasitic capacitance aswill be described below.

FIG. 13 illustrates an exemplary close up view of the stack-up depictedin FIG. 12. Touch pixel electrodes 1302 and 1304 can be patterned on ITOlayer 1208. Touch pixel electrodes 1302 and 1304 can be coupled to sensecircuitry 1306 and 1308 respectively, and the sense circuitry can becoupled to a stimulation source 1310 to operate in a self-capacitancetouch sensor configuration as described above. Due to their proximity tothe cathode layer 1212, touch pixel electrodes 1302 and 1304 mayexperience a parasitic capacitance arising from the interaction betweenthe touch pixel electrodes and the cathode layer as depicted bycapacitances 1312 and 1314. This parasitic capacitance may cause currentto flow from the sense circuitry 1306 and 1308 towards the individualtouch pixel electrodes 1302 and 1304. This current flow can waste analogsignal dynamic range at the outputs of sense circuitry 1306 and 1308. Inorder to mitigate the phenomenon described above, cancellation circuits1316 and 1318 can be coupled to the touch pixel electrodes 1302 and1304. Cancellation circuits 1316 and 1318 can produce current that canbe injected into the touch circuit such that any current flows generatedby a parasitic capacitance can be offset such that the effect of theparasitic capacitance is cancelled. The cancellation circuits 1316 and1318 can be set during an initial calibration, while no touch event isoccurring, to ensure that any currents generated by parasiticcapacitances are cancelled. Finally, the cathode layer can be ACgrounded to further limit the parasitic capacitance seen by the touchcircuitry.

FIG. 14 illustrates an exemplary time line for operating the device in atouch detection mode and a display operation mode. As illustrated, atouch detection mode 1402 can be alternated with a display operationmode 1404 such that the two modes are mutually exclusive in time. Inother words, the two modes 1402 and 1404 can be multiplexed in time. Theduration in time of each mode can vary and can depend on other functionsof the device. For example, the touch detection mode can occur while thedisplay is in a vertical blanking mode as is known in the art. Further,touch may be detected (e.g., the touch sensor panel may be scanned fortouch) one or more times during touch mode 1402. In addition, althoughexamples herein may describe the display circuitry as operating during adisplay operation, and describe the touch sensing circuitry as operatingduring a touch sensing operation, it should be understood that a displayoperation and a touch sensing operation may be operated at the sametime, e.g., partially or completely overlap, or the display operationand touch phase may operate at different times.

Also, although examples herein describe certain circuit elements asbeing multi-function and other circuit elements as beingsingle-function, it should be understood that the circuit elements arenot limited to the particular functionality in other examples. In otherwords, a circuit element that is described in one example herein as asingle-function circuit element may be configured as a multi-functioncircuit element in other examples, and vice versa.

Although examples of this disclosure have been fully described withreference to the accompanying drawings, it is to be noted that variouschanges and modifications including, but not limited to, combiningfeatures of different examples, omitting a feature or features, etc., aswill be apparent to those skilled in the art in light of the presentdescription and figures.

For example, one or more of the functions of computing system 200described above can be performed by firmware stored in memory (e.g. oneof the peripherals 204 in FIG. 2) and executed by touch processor 202,or stored in program storage 232 and executed by host processor 228. Thefirmware can also be stored and/or transported within any non-transitorycomputer-readable storage medium (not including signals) for use by orin connection with an instruction execution system, apparatus, ordevice, such as a computer-based system, processor-containing system, orother system that can fetch the instructions from the instructionexecution system, apparatus, or device and execute the instructions. Inthe context of this document, a “non-transitory computer-readablestorage medium” can be any medium other than a signal that can containor store the program for use by or in connection with the instructionexecution system, apparatus, or device. The non-transitory computerreadable storage medium can include, but is not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus or device, a portable computer diskette(magnetic), a random access memory (RAM) (magnetic), a read-only memory(ROM) (magnetic), an erasable programmable read-only memory (EPROM)(magnetic), a portable optical disc such a CD, CD-R, CD-RW, DVD, DVD-R,or DVD-RW, or flash memory such as compact flash cards, secured digitalcards, USB memory devices, memory sticks, and the like.

The firmware can also be propagated within any transport medium for useby or in connection with an instruction execution system, apparatus, ordevice, such as a computer-based system, processor-containing system, orother system that can fetch the instructions from the instructionexecution system, apparatus, or device and execute the instructions. Inthe context of this document, a “transport medium” can be any mediumthat can communicate, propagate or transport the program for use by orin connection with the instruction execution system, apparatus, ordevice. The transport readable medium can include, but is not limitedto, an electronic, magnetic, optical, electromagnetic or infrared wiredor wireless propagation medium.

Examples may be described herein with reference to a Cartesiancoordinate system in which the x-direction and the y-direction can beequated to the horizontal direction and the vertical direction,respectively. However, one skilled in the art will understand thatreference to a particular coordinate system is simply for the purpose ofclarity, and does not limit the direction of the elements to aparticular direction or a particular coordinate system. Furthermore,although specific materials and types of materials may be included inthe descriptions of examples, one skilled in the art will understandthat other materials that achieve the same function can be used. Forexample, it should be understood that a “metal layer” as described inthe examples below can be a layer of any electrically conductivematerial.

In some examples, the drive lines and/or sense lines can be formed ofother elements including, for example other elements already existing intypical LCD displays (e.g., other electrodes, conductive and/orsemiconductive layers, metal lines that would also function as circuitelements in a typical LCD display, for example, carry signals, storevoltages, etc.), other elements formed in an LCD stackup that are nottypical LCD stackup elements (e.g., other metal lines, plates, whosefunction would be substantially for the touch sensing system of thetouch screen), and elements formed outside of the LCD stackup (e.g.,such as external substantially transparent conductive plates, wires, andother elements). For example, part of the touch sensing system caninclude elements similar to known touch panel overlays.

Although various examples are described with respect to display pixels,one skilled in the art would understand that the term display pixels canbe used interchangeably with the term display sub-pixels in examples inwhich display pixels are divided into sub-pixels. For example, someexamples directed to RGB displays can include display pixels dividedinto red, green, and blue sub-pixels. In other words, in some examples,each sub-pixel can be a red (R), green (G), or blue (B) sub-pixel, withthe combination of all three R, G and B sub-pixels forming one colordisplay pixel. One skilled in the art would understand that other typesof touch screen could be used. For example, in some examples, asub-pixel may be based on other colors of light or other wavelengths ofelectromagnetic radiation (e.g., infrared) or may be based on amonochromatic configuration, in which each structure shown in thefigures as a sub-pixel can be a pixel of a single color.

Therefore, according to the above, some examples of the disclosure aredirected to a touch sensitive device including a plurality of displaypixels, the touch sensitive device comprising: a TFT layer, the TFTlayer comprising a plurality of circuit elements that are configurableas a plurality of self-capacitance touch pixel electrodes during a touchdetection mode of the device, and are configurable as display circuitryduring a display mode of the device, wherein each of the plurality ofself-capacitance touch pixel electrodes is electrically isolated fromothers of the plurality of self-capacitance touch pixel electrodes, andwherein each of the plurality of self-capacitance touch pixel electrodesrepresents a unique touch location on a touch sensor panel; a pluralityof conductive wires, each wire of the plurality of conductive wiresconfigured to transmit a touch signal from one of the plurality ofcircuit elements to a touch controller of the device; and one or moreprocessing units configured to switch the device between the touchdetection mode and the display mode, wherein during the touch detectionmode, the plurality of circuit elements are configured asself-capacitance touch pixel electrodes, and during the display mode,the plurality of circuit elements are biased at a common voltage.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, the one or more processing units comprise thetouch controller. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the touch controllercomprises a plurality of sense circuits, and the plurality of conductivewires are configured to transmit the touch signals to the plurality ofsense circuits. Additionally or alternatively to one or more of theexamples disclosed above, in some examples, the touch detection mode ofthe device and the display mode of the device are time multiplexed.Additionally or alternatively to one or more of the examples disclosedabove, in some examples, a first conductive wire of the plurality ofconductive wires has a first width and a first length, and a secondconductive wire of the plurality of conductive wires has a second widthand a second length, the second length being greater than the firstlength, the second width being greater than the first width such that afirst resistance of the first conductive wire is substantially equal toa second resistance of the second conductive wire, Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the device further comprises a wire matrix disposed in anon-active area of a display comprising the plurality of display pixels,the wire matrix configured to transmit display control signals to theplurality of display pixels during the display mode.

Some examples of the disclosure are directed to an organic lightemitting diode (OLED) touch sensitive device including a plurality ofdisplay pixels, the device comprising: an anode layer; and a cathodelayer, the cathode layer comprising a plurality of circuit elements thatare configurable as a plurality of self-capacitance touch pixelelectrodes during a touch detection mode of the device, and areconfigurable as a cathode for an OLED display during a display mode ofthe device, wherein each of the plurality of self-capacitance touchpixel electrodes is electrically isolated from others of the pluralityof self-capacitance touch pixel electrodes, and wherein each of theplurality of self-capacitance touch pixel electrodes represents a uniquetouch location on a touch sensor panel. Additionally or alternatively toone or more of the examples disclosed above, in some examples, thedevice further comprises: a stimulation circuit, the stimulation circuitconfigured to stimulate the self-capacitance touch pixel electrodesduring the touch detection mode of the device; and a bootstrappingcircuit, the bootstrapping circuit configured to stimulate the anodelayer of the device with substantially the same signal as being used bythe stimulation circuit to stimulate the self-capacitance touch pixelelectrodes during the touch detection mode of the device. Additionallyor alternatively to one or more of the examples disclosed above, in someexamples, the anode layer comprises a plurality of anode elements, andduring the display mode of the device, each of the plurality of circuitelements is electrically coupled to a respective anode element of theplurality of anode elements. Additionally or alternatively to one ormore of the examples disclosed above, in some examples, each of theplurality of circuit elements is electrically coupled to a respectiveanode element of the plurality of anode elements via an organic layercomprising a plurality of organic light emitting diodes, Additionally oralternatively to one or more of the examples disclosed above, in someexamples, a DC current between the anode layer and the self-capacitancetouch pixel electrodes remains substantially constant during the touchdetection mode of the device. Additionally or alternatively to one ormore of the examples disclosed above, in some examples, the touchdetection mode of the device and the display mode of the device are timemultiplexed.

Some examples of the disclosure are directed to an organic lightemitting diode touch sensitive device including a plurality of displaypixels, the device comprising: a cathode layer; an ITO layer, the ITOlayer configurable as a plurality of self-capacitive touch sensorsduring a touch detection mode of the device, and configurable as ananode layer during a display mode of the device, wherein each of theplurality of self-capacitive touch sensors is electrically isolated fromothers of the plurality of self-capacitive touch sensors, and whereineach of the plurality of self-capacitive touch sensors represents aunique touch location on a touch sensor panel; and an encapsulationlayer disposed between the cathode layer and the ITO layer. Additionallyor alternatively to one or more of the examples disclosed above, in someexamples, the device further comprises: a metal layer, the metal layerconnected to the ITO layer through a plurality of vias. Additionally oralternatively to one or more of the examples disclosed above, in someexamples, the device further comprises: a cancellation circuit, thecancellation circuit coupled to the ITO layer and configured to cancel aparasitic capacitance effect of one or more of the self-capacitive touchsensors. Additionally or alternatively to one or more of the examplesdisclosed above, in some examples, the parasitic capacitance effectcomprises an offset current, and the cancellation circuit is configuredto cancel the parasitic capacitance effect by at least producing anoffset cancellation current to offset the offset current. Additionallyor alternatively to one or more of the examples disclosed above, in someexamples, an operation of the cancellation circuit is determined when notouch event is occurring at the device. Additionally or alternatively toone or more of the examples disclosed above, in some examples, the touchdetection mode of the device and the display mode of the device are timemultiplexed.

Although the disclosed examples have been fully described with referenceto the accompanying drawings, it is to be noted that various changes andmodifications will become apparent to those skilled in the art. Suchchanges and modifications are to be understood as being included withinthe scope of the disclosed examples as defined by the appended claims.

What is claimed is:
 1. An organic light emitting diode touch sensitivedisplay including a plurality of display pixels, the display comprising:an electrode layer including a plurality of self-capacitance touchsensor electrodes, wherein each of the plurality of self-capacitancetouch sensor electrodes is electrically isolated from others of theplurality of self-capacitance touch sensor electrodes; a cathode layerthat is coupled to AC ground during a touch detection mode of thedisplay and is configured to reduce a parasitic capacitance effect onthe plurality of self-capacitance touch sensor electrodes, wherein theparasitic capacitance effect includes an effect from capacitive couplingbetween the plurality of self-capacitance touch sensor electrodes andthe cathode layer, and reducing the parasitic capacitance effectincludes reducing the capacitive coupling between the plurality ofself-capacitance touch sensor electrodes and the cathode layer; an anodelayer; an organic layer, the organic layer including a plurality oforganic light emitting diodes; and an encapsulation layer disposedbetween the cathode layer and the electrode layer.
 2. The display ofclaim 1, wherein the touch detection mode of the display and a displaymode of the display are time multiplexed.
 3. The display of claim 1,further comprising: a metal layer, the metal layer connected to theelectrode layer through a plurality of vias.
 4. The display of claim 1,further comprising: a cancellation circuit, the cancellation circuitcoupled to the electrode layer and configured to cancel a parasiticcapacitance effect of one or more of the self-capacitance touch sensorelectrodes.
 5. The display of claim 4, wherein: the parasiticcapacitance effect comprises an offset current, and the cancellationcircuit is configured to cancel the parasitic capacitance effect by atleast producing an offset cancellation current to offset the offsetcurrent.
 6. A method of operating an organic light emitting diode touchsensitive display including a plurality of display pixels, the methodcomprising: providing: an electrode layer including a plurality ofself-capacitance touch sensor electrodes, wherein each of the pluralityof self-capacitance touch sensor electrodes is electrically isolatedfrom others of the plurality of self-capacitance touch sensorelectrodes; an anode layer; an organic layer, the organic layerincluding a plurality of organic light emitting diodes; and anencapsulation layer disposed between a cathode layer and the electrodelayer; and coupling the cathode layer to AC ground during a touchdetection mode of the display, wherein the cathode layer is configuredto reduce a parasitic capacitance effect on the plurality ofself-capacitance touch sensor electrodes, wherein the parasiticcapacitance effect includes an effect from capacitive coupling betweenthe plurality of self-capacitance touch sensor electrodes and thecathode layer, and reducing the parasitic capacitance effect includesreducing the capacitive coupling between the plurality ofself-capacitance touch sensor electrodes and the cathode layer.
 7. Themethod of claim 6, further comprising time multiplexing the touchdetection mode of the display and a display mode of the display.
 8. Themethod of claim 6, further comprising providing a metal layer, the metallayer connected to the electrode layer through a plurality of vias. 9.The method of claim 6, further comprising: canceling a parasiticcapacitance effect of one or more of the self-capacitance touch sensorelectrodes using a cancellation circuit coupled to the electrode layer.10. The method of claim 9, wherein the parasitic capacitance effectcomprises an offset current, the method further comprising canceling theparasitic capacitance effect by at least producing an offsetcancellation current, using the cancellation circuit, to offset theoffset current.
 11. An electronic device comprising: a processor;memory; and an organic light emitting diode touch sensitive displayincluding a plurality of display pixels, the display comprising: anelectrode layer including a plurality of self-capacitance touch sensorelectrodes, wherein each of the plurality of self-capacitance touchsensor electrodes is electrically isolated from others of the pluralityof self-capacitance touch sensor electrodes; a cathode layer that iscoupled to AC ground during a touch detection mode of the display and isconfigured to reduce a parasitic capacitance effect on the plurality ofself-capacitance touch sensor electrodes, wherein the parasiticcapacitance effect includes an effect from capacitive coupling betweenthe plurality of self-capacitance touch sensor electrodes and thecathode layer, and reducing the parasitic capacitance effect includesreducing the capacitive coupling between the plurality ofself-capacitance touch sensor electrodes and the cathode layer; an anodelayer; an organic layer, the organic layer including a plurality oforganic light emitting diodes; and an encapsulation layer disposedbetween the cathode layer and the electrode layer.
 12. The device ofclaim 11, wherein the touch detection mode of the display and a displaymode of the display are time multiplexed.
 13. The device of claim 11,further comprising: a metal layer, the metal layer connected to theelectrode layer through a plurality of vias.
 14. The device of claim 11,further comprising: a cancellation circuit, the cancellation circuitcoupled to the electrode layer and configured to cancel a parasiticcapacitance effect of one or more of the self-capacitance touch sensorelectrodes.
 15. The device of claim 14, wherein: the parasiticcapacitance effect comprises an offset current, and the cancellationcircuit is configured to cancel the parasitic capacitance effect by atleast producing an offset cancellation current to offset the offsetcurrent.